Asteroid risk real, says former astronaut

Russia's recent space rock explosion could have been much worse, according to proponents of an asteroid-detecting space telescope.

By Henry Fountain

March 21, 2013 — 10.47am

Making a case for the need to detect asteroids before they hit Earth, a former astronaut said on Wednesday that the number of casualties would have been enormous had the space rock that exploded in Russia last month blown apart directly over New York City in–stead.

"We'd have a lot more than broken windows, that's for sure," the former astronaut, Edward Lu, told a Senate panel in Washington.

"Right now, the amount of warning time that we are likely to get from one of these asteroids is zero": B612 Foundation's Edward Lu of the space rock explosion over Chelyabinsk, Russia.Credit:AP

Lu, also a former Google executive, is now the chief executive of the B612 Foundation, a Silicon Valley group that wants to build a privately financed asteroid-detecting space telescope.

About 1500 people were injured when the roughly 18-metre-diameter meteor exploded high in the atmosphere near the Russian city of Chelyabinsk on February 15. Most of the injuries were caused by flying glass from shattered windows when a shock wave from the explosion – estimated to have been about 30 times more powerful than the atomic bomb that destroyed Hiroshima – hit the city a minute and a half later.

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"Had that shock wave been a lot closer to a city, it would have caused a lot more damage," Lu said.

He also noted that if the Tunguska event – the explosion of a roughly 46-metre asteroid over Siberia in 1908 – had occurred over New York, "whatever the population of New York City is, they'd be gone".

The Chelyabinsk meteor was not detected by any of the ground-based telescopes, operated by NASA and others, that are surveying the sky for space rocks that are in orbits that could intersect with Earth's. Those search programs are focused on larger asteroids, James Green, director of the planetary science division of the National Aeronautics and Space Administration, told the Senate panel, the Science and Space Subcommittee.

So far about 10,000 have been detected, including about 95 per cent of the estimated 1100 that are a kilometre or more in diameter and have the potential to end civilisation. So far, Green said, no asteroid has been found that poses a threat to the planet.

But Lu noted that for every asteroid that had been detected, there were probably 100 more that had not been seen, including hundreds of thousands that are the size of the Russian meteor.

"Right now, the amount of warning time that we are likely to get from one of these asteroids is zero," he said.

If a meteor were found to be just days from hitting Earth, there is little that could be done, except perhaps evacuating a city or region. But in response to a question from Senator Ted Cruz of Texas, the ranking Republican on the subcommittee, Lu said that given enough lead time, there were various ways to divert an asteroid to make it miss Earth entirely, including something as basic as running into it with a spacecraft to nudge it just a bit.

"If you find it early, we have many options," Lu said. "Then you only need to change its trajectory by a very tiny amount."

"The key is, if you don't know where they are, there's nothing you can do."

While some people argue that money would be better spent on more pressing societal problems than on a low-probability event like a civilisation-busting asteroid strike, both Mr Cruz and Senator Bill Nelson, the Florida Democrat who is chairman of the panel, expressed little scepticism about the scientists' testimony.

"I'm eager for our collective journey to insure that NASA and all related programs have sufficient resources and sufficient priorities to do what needs to be done," said Mr Cruz, who was elected last year with Tea Party backing, in his opening remarks.

Asked after the hearing about the senator's position on the NASA budget, only a small portion of which goes toward asteroid detection, a spokeswoman for Cruz said she had no comment.

One difficulty in searching for asteroids from the ground is that the sun often gets in the way, making a small space rock impossible to see. The B612 telescope, called Sentinel, would be oriented in a way that could eliminate that problem. The project is estimated to cost $US450 million, and the foundation has a goal of launching the telescope within five years.

While NASA is not providing any money for the Sentinel project, Green said the agency was offering some technical help.

In a later interview, Lu said that while his group was busy raising money privately and was not seeking money from NASA, "if they decide that this is something that is of value to them, and they want to have that conversation, then I'd be happy to have that conversation".